Astro Physics Question:

WHAT ARE THE FORCES WHICH KEEP A FLYING PLANE IN A EQUILIBRIUM?

Answer:

for level flight lift is balanced by weight and thrust is
balanced by drag, hence then whole system become stable
w.r.t to force and for moments , inherently stable aircraft
are designed in a way that the pitching moment is balanced
by horizontal stabilizer , elevator may be deflected for
trim at certain velocities where i'm not changing the moment
curve slope , and for roll and yaw stability both aileron
and rudder may be used as they are cross coupled. Aids in
roll and yaw stability may be provided by high wing, sweep
back, dihedral wings etc